The present disclosure relates roll bending machines having three or four rolls, which are well known in the metal fabricating industry for rolling metal plate into cylinders, obrounds and cone shapes. This type of machine uses hydraulic cylinders to change the relative position between the various rolls of the machine, and also hydraulic motors to rotate the rolls, such that plates can be formed in any desired shape.
The hydraulic systems of such machines commonly utilize a centrally located hydraulic manifold on which proportional valves, counterbalance valves, solenoid valves, flow control valves, oil pressure sensors and the like are mounted to operate hydraulic cylinders or motors that power and position gripping and bending rolls. In certain machines, the hydraulic manifolds are manufactured to National Fluid Power Association (NFPA) standard dimensions or International Standard Organization (ISO) standard dimensions and can be purchased from catalogs of various manufacturers. Similarly, the cylinders are manufactured to NFPA or ISO standard dimensions and can be purchased from catalogs form various manufacturers.
In a typical roll bending machine, pressurized hydraulic fluid is provided from a hydraulic pump into a manifold, which contains valves and other flow control devices that are fluidly connected, via tubes and hoses, to the various actuators of the machine. As is often the case, when an actuator is to be activated, a valve will open to port hydraulic fluid under pressure to the actuator; in other words, the pressurized fluid is conveyed to the actuator via piping that interconnects the manifold with the actuator. Depending on the location of the actuator on the machine, the piping may have to traverse a relatively short or relatively long distance before reaching the actuator.
In the past, machine designers have tried to place the manifold at a central location on the machine such that actuators that are required to be active simultaneously, for example, pairs of cylinders operating to adjust the position of a bending roll, are activated simultaneously and without delays. Nevertheless, it is not always practical to place the manifold in a location where all actuators on the machine are at equal distances. As a result, oil to one of the actuators often has to travel a longer or shorter distance than oil provided to the other actuator in a pair, based on the location of the actuators on the machine, which can cause imbalances during operation. Further, the oil is provided to the various actuators using different types of fluid conduits, for example, hard metal tubes or flexible rubber hoses, which introduces further imbalances to the system. Lastly, the temperature and resulting changes in compressibility of the hydraulic fluid, when the activating fluid has to travel relatively large distances before it acts on an actuator, introduces elasticity and vibration in the system.